FBI Director James Comey on Wednesday offered his most forceful defense yet of his highly controversial decision to disclose the reopening of the Hillary Clinton email investigation 11 days before last fall's presidential election.

Testifying before the Senate Judiciary Committee, Comey said he faced an agonizing choice at the time about whether to sit on the potentially momentous development or share it with Congress. He chose to tell Congress — a move that many Democrats and political analysts believe delivered the White House to Donald Trump.

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"This was terrible. It made me mildly nauseous to think that we might have had some impact on the election, but honestly, it wouldn't change the decision," Comey said.

"We honestly made a decision between those two, those two choices, that even in hindsight — and this has been one of the world's most painful experiences — I would make the same decision. I would not conceal that, on Oct. 28, from the Congress. ... I knew there'd be a huge storm that would come."

Comey's testimony was the most expansive and detailed insight the FBI chief has offered into his thinking during the days before the election, but it seemed to do little to quiet Democratic senators' concerns that he applied a double standard that resulted in Clinton being kneecapped in advance of the vote even though the FBI was also — without public notice —conducting a politically explosive investigation into the Trump campaign's possible collusion with Russia.

However, the sense of rectitude Comey displayed may give Democrats some solace that the ongoing Trump-Russia probe will be pursued wherever it may lead.

Toward the end of Wednesday's four-hour hearing, Comey briefly suggested that some of the disagreement critics have expressed with his election-eve decision about the email probe might be insincere.

"I don’t think many reasonable people would do it differently no matter what they say today," the FBI chief said.

Comey insisted that the emails discovered on a laptop belonging to ex-Rep. Anthony Weiner weeks before the election could have contained crucial information related to the Clinton probe. The FBI chief said that many of them initially appeared to be from a time in 2009 when thousands of Clinton's messages were missing. He also said he believed that messages from those months at the outset of Clinton's tenure as secretary of state could be particularly important because they might indicate why the private email account was set up.

Comey said he'd normally keep such an investigative move secret but ultimately concluded he had a duty to keep Congress informed, as he said he would in earlier testimony.

"'Speak' would be really bad. There's an election in 11 days. Lordy, that would be really bad," he recalled thinking. "Concealing, in my view, would be catastrophic, not just to the FBI but well beyond, and, honestly, as between really bad and catastrophic, I said to my team, we've got to walk into the world of really bad."

Comey acknowledged "a great debate" among his advisers but said they all agreed with his ultimate decision. He said one junior attorney on his team did ask at the time if they should consider whether the disclosure to the Hill would tip the election to Trump.

Comey said his instincts as an ex-prosecutor were not to do anything that might affect an election, but he concluded that worrying about electing Trump would be wrong to even consider. "Not for a second," he said he replied to the junior FBI attorney asking whether that should be factored in. "Down that path lies the death of the FBI."

As it turned out, the newly discovered emails were not momentous. There were about 40,000 in all — 3,000 of which were related to official State Department work. Just 12 were deemed classified, although Comey acknowledged they should not have been accessible to Weiner, who lacked a security clearance.The FBI chief also disclosed that his investigators turned out to be wrong about something else: how long it would take to pore through the messages. He said they initially told him there was no chance they could finish before the election, but a computer program the FBI compiled ultimately culled out duplicate messages and had the task completed in just a week.

"We'd seen them all before," Comey said of the messages.

The timing issue is pivotal because had Comey known that the work could be done in advance of the election, he might have waited to notify Congress once the content of the messages was clear. Instead, he sounded what many Democrats regard as a false alarm that deflated Clinton's campaign. The Senate hearing came just a day after Clinton said during a public interview that she believed the FBI's action affected the outcome of the election — although she framed it as the combined effect of those disclosures and the hacking and public release of her campaign chairman John Podesta's email account, allegedly by individuals working for Russian interests.

"I was on the way to winning until a combination of Jim Comey’s letter on October 28th and Russian WikiLeaks raised doubts in the minds of people who were inclined to vote for me but got scared off," Clinton said. “And the evidence for that intervening event is, I think, compelling, persuasive.”

Trump on Tuesday night responded on Twitter by accusing the FBI chief of having gone easy on Clinton over the classified emails found in her private account.

"FBI Director Comey was the best thing that ever happened to Hillary Clinton in that he gave her a free pass for many bad deeds!" Trump wrote.

When asked by Sen. Sheldon Whitehouse (D-R.I.) to comment on the president's claim Clinton had gotten a "free pass," Comey said that wasn't his view.

"No. ... That was not my intention, certainly," the FBI director replied.

At another point in the hearing, Comey said his decision to announce the initial outcome of the Clinton email probe last summer was cemented by Attorney General Loretta Lynch's so-called tarmac meeting with former President Bill Clinton on June 27 at the Phoenix airport.

"I'm not picking on the attorney general, Loretta Lynch ... but her meeting with President Clinton on that airplane was the capper for me. I then said, 'You know what? The department cannot by itself credibly end this,'" Comey said.

The FBI director said that development, along with other information he said he could not discuss publicly, led him to decide to disclose the outcome of the Clinton probe without advance permission from Justice Department officials. He said he did call Lynch the day of his announcement to tell her of his general plan but not what he would say.

"That was a hard call for me to make, to call the attorney general that morning and say, 'I'm about to do a press conference and not going to tell you what I'm going to say.' I said, 'I hope someday you understand why I'm doing this,'" Comey said. "I knew this would be disastrous for me personally, but I thought it was the best way to protect the institutions we care about."

During the hearing, the FBI chief found himself slammed by both political camps, with Democratic senators accusing him of tipping the balance in the 2016 presidential election and Republicans questioning the FBI's reliance on a shadowy dossier of salacious allegations against Trump.

At the outset of the hearing, Chairman Chuck Grassley (R-Iowa) suggested that there's little substance to the story that has dominated Washington in recent months — allegations of coordination between the Trump campaign and the Russian government.

"Where is all this speculation about collusion coming from?" Grassley asked, as he raised reports that the FBI actually paid the author of the dossier, which included allegedly compromising intelligence against Trump.

"Where did the money come from, and what motivated the people writing [the dossier]?" he said. "Unfortunately, the FBI has provided me materially inconsistent information about these issues," the chairman complained. "Once you buy into the claim of collusion, then suddenly every interaction with a Russian can be twisted to seem like confirmation of a conspiracy theory."

The top Democrat on the panel, Sen. Dianne Feinstein of California, accused Comey of using a double standard that resulted in damaging official disclosures about Clinton during the campaign but left the investigation into Russia and the Trump campaign largely in the shadows.

"I join those who believe that the actions taken by the FBI did in fact have an impact on the election," Feinstein said. "I cannot help but note that [the FBI] was noticeably silent about the investigation into the Trump campaign and Russian interference in the election. ... I can't imagine how an unprecedented big and bold hacking interference in our election by the Russian government did not also present exceptional circumstances."

Sen. Patrick Leahy (D-Vt.) also said Comey's Oct. 28 letter to Congress about the Clinton probe had clearly roiled the campaign.

"There's no question that that had great effect. Historians can debate what kind of effect it was," Leahy said.

Comey said the probes were treated similarly in that both inquiries were not publicly confirmed until several months after they were underway.

"I think I've treated both investigations consistently under the same principles, " the FBI director said.

Sen. Chris Coons (D-Del.) rejected Comey's claim that he had only two options last October.

"I do think there was a third door available to you, and that was to confirm the existence of an ongoing investigation about the Trump campaign," Coons declared. "Had there been public notice that there was renewed investigation into both campaigns, I think the impact would have been different."

Comey said he did favor calling the public's attention in general terms to the Russian efforts and actually proposed writing an op-ed on the issue last August. The Obama White House turned that down, opting to make findings of a broad intelligence assessment public some two months later.

"I thought it was very important myself to call out Russia," the FBI director said. "That's a separate question from whether — do you confirm the existence of the classified investigation that had just started. … We don’t know what we have, what is there."

Some Republicans were more generous in their assessment of Comey's decisionmaking at the height of the presidential campaign.

"I think you were given an impossible choice to make and you did the best you could," Sen. John Cornyn of Texas said.

"It looks like you were trying to provide as much transparency and as much real-time information as you had," Sen. Thom Tillis of North Carolina added.

However, some GOP senators pressed Comey on why no charges were filed against Clinton aide Huma Abedin, even though emails deemed to be classified were found on the laptop of her estranged husband, Weiner.

"We didn’t have any indication that she had a sense that what she was doing was in violation of the law — to provide any sort of criminal intent," Comey said. He said Abedin apparently sent the messages to Weiner so he could print them for her.

"My understanding is his role was to print them out as a matter of convenience," the FBI director said. He did not indicate whether any of the messages were marked classified.

Comey also said that he's determined to get to the bottom of who may have leaked sensitive information about the Clinton email probe or the Trump-Russia inquiry, including whether former FBI officials or prosecutors were given inside details about the investigations.

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"Leaks are always a problem, particularly in the last three to six months," the FBI chief said. "If I find out that people were leaking information about our investigation, whether to reporters or private parties, there will be severe consequences. … It’s a matter that I’m very, very interested in."

Comey also disclosed Wednesday that former acting Attorney General Sally Yates discussed with him her concerns that former national security adviser Michael Flynn was giving Trump’s White House inaccurate information about his contacts with the Russian ambassador.

Under questioning from Sen. Lindsey Graham (R-S.C.), Comey confirmed he discussed the issue with Yates, who is set to testify about the issue next week before a Senate subcommittee chaired by Graham.

Yates is expected to tell senators she delivered a strong and unusual warning to the White House in January that Flynn had lied about his contacts with Russia and was vulnerable to being compromised. Flynn was ousted by Trump less than a month later after it became public that he had misled his colleagues about his phone conversations with Russian ambassador Sergey Kislyak.